A technology has been proposed in which when IC (Integrated Circuits) chips and other electronic parts are mounted on a circuit board, a conductive material such as a solder and the like is previously subjected to coating (potting) on predetermined positions of the circuit board, electronic parts are provided at the positions and then the resulting circuit board is subjected to reflow treatment (heating treatment) to melt the conductive material to mount the electronic parts on the circuit board. (Refer to Patent Document 1, for example.) According to the technique, it is possible to manufacture electronic modules at low cost.
In recent years, a technique has been proposed in which on a circuit board on which an optical element has been provided in addition to electronic parts has been subjected to reflow treatment as described above, whereby the electronic parts and the optical element are simultaneously mounted on the circuit board, resulting in an electronic module united with the optical element. Thus, further improvement in production efficiency of an optical device production system has been sought. When an optical device is produced by the production system to which the reflow treatment as described above is introduced, it is desired that an inexpensive plastic material be used as a material constituting the optical device in place of an expensive glass material.
It is considered that a thermoplastic resin is used as the plastic material which is easy to process and mold, and has good light transmittance, however, an optical element molded from the thermoplastic resin has a defect that it is likely to deform by heat, since the thermoplastic resin is softened and melted at a relatively low temperature. When an optical element and electronic parts are simultaneously mounted on a circuit board according to the reflow treatment, the optical element composed of the thermoplastic resin is likely to deform and is difficult to show the original optical properties, since the optical element itself is subjected to heating treatment at around 260° C.
In view of the above, the present inventors have studied a heat curable resin as a plastic material used in an optical element which is durable to the reflow treatment. A heat curable resin before curing is in the form of liquid or shows fluidity, and has good processability and moldability like a thermoplastic resin, and a heat curable resin after curing loses fluidity unlike a thermoplastic resin, minimizing deformation due to heat. Among heat curable resins, particularly an acryl resin having an alicyclic structure has excellent heat resistance and therefore, is considered to be a preferred material for an optical element.    Patent Document 1: Japanese Patent O.P.I. Publication No. 2001-24320    Patent Document 2: Japanese Patent O.P.I. Publication No. 2006-315960